Known mowing knife drives are realized in different types of construction. Especially for mowing knives for large mowing widths, particularly with width of up to 18 meters, i.e. where high performance is needed. Such drive units include one gearing unit that converts a rotational movement directly into a reciprocating movement. The drive unit is directly operatively connected to oscillatingly drive the knife head of the mowing knife.
U.S. Pat. No. 6,273,214 B1 shows an angular gear arrangement to drive a cutting knife. In this case, a first gearing unit is provided. The unit converts a rotational movement into a translatory movement to drive the cutting knife. Furthermore, a second gearing unit is provided in the form of an angular gearing. The second gearing unit changes the direction of rotation. The drive unit is driven by a motor arranged at a distance, via a belt drive and a pulley. In this case, the rotation of the pulley, which rotates around a horizontal axis, is transferred into a rotational movement around a vertical axis. Thus, the second gearing unit is in the form of an angular gearing.
A gearing unit to drive a cutting knife is further described in DE 36 15 058 C2. The unit has a housing that forms a first axis. The gearing unit has a rotor rotatably supported in the housing around the first axis. It is driven by a drive aggregate. In the housing, a ring gear with internal teeth is stationarily mounted. Thus, it does not rotate relative to the housing. The rotor is held in bearings in the housing. On the rotor itself, a pinion is further rotatably supported around a second axis. The second axis is radially off-set to the first axis. The pinion forms the output element of the gearing and meshes with a ring gear.
In practice, such a gearing unit is driven by a belt drive from a drive motor. Additionally, a flywheel is often provided to enable operations with sudden occurring loadings. Furthermore, hydraulic motors are used for the drive. However, these drive units need a large space. The maximal mowing width is reduced as these drive units are arranged laterally to the cutting knife in an axial extension of the direction of movement of the cutting knife. Accordingly, the drives are arranged externally at the ends of the cutting knives. Thus, special precautions are taken to enable support of large weights of the drives at the outside.
A drive for a cutting device is shown in DE 10 2009 040 230 B4. Here, a cutting knife is driven by a gearing, as shown in FIG. 1. The cutting device is for an agricultural machine schematically shown in FIG. 1. It has a gearing 10 that drives a cutting knife 12. For clarity, the cutting knife 12 is only partially shown in FIG. 1. The cutting knife 12 can be a mowing knife of a harvesting machine, like a combine harvester. The gearing 10 is preferably stationarily mounted on the cutter bar that guides the cutting knife.
A countershaft 14 is shown schematically in FIG. 1. The countershaft 14 drives a crank drive 16, the gearing 10 and the cutting knife 12. The countershaft 14 extends transversally to the driving direction of the agricultural machine and is rotatingly driven.
The gearing 10 has a housing 18 of which a half shell is schematically shown in FIG. 1. A rocker 20 is accommodated in the housing 18. The rocker 20 can carry out a rocking movement in a plane corresponding to the drawing plane. A concave guide contour 22 is formed on an inner side on the wall of the housing 18. The concave guide contour 22 extends along an arc around a gearing-side fixed point 24 and corresponds, in the shown example, to an approximate quadrant.
The rocker 20 has a convex arc-like outer contour 26. The rocker outer contour 26 extends around a guide point 28 of the rocker 20. The outer contour 26 corresponds, at least more or less, to half a circle. In this case the outer contour 26 has a radius R. The guide contour 22 has a radius of 2R. The outer contour 26 and the guide contour 22 include teeth that engage each other. Thus, the rocker 20 meshes with the guide contour 22 and is restricted to roll on the guide contour 22.
To prevent lifting of the rocker 20 from the guide contour 22, the rocker is connected in an articulated manner at the guide point 28 to a guide rod 30. The guide rod 30 is connected in an articulated manner at the gearing-side fixed point 24 to the housing 18. The distance between the gearing-side fixed point 24 and the guide point 28 is approximately R. Thus, a restricted guidance is provided of the guide point 28 on the arc with the radius R around the gearing fixed point 24. Alternatively, the guide rod 30 can be substituted by a roller. The roller is rotatably supported around the guide point and rolls on a convex guide crank around the gearing-side fixed point 24.
A driving hinge point 34 and an output hinge point 32 of the rocker 20 are arranged at a distance of approximately R away from the guide point 28. Rolling of the rocker 20 on the guide contour 22 (rocking movement) causes a rectilinear reciprocating movement in the direction toward the gearing-side fixed point 24 and away from the same. The guide rod 30 and the teeth force a linear guidance of the hinge points 32, 34.
At output element 36, in the form of a rod, is connected in an articulated manner to the rocker 20 at the output hinge point 32. The output element 36 is guided out of the housing 18 in a loose manner in a straight line. It is sealed by a convoluted boot 38. The output element 36 is connected in an articulated manner, via a holder 40, to allow alignment compensation, to the cutting knife 12. The longitudinal extension of the cutting knife 12 is parallel to the direction of the reciprocating movement of the output hinge point 32. Small alignment errors between the cutting knife 12 and the point 32 can be compensated by articulation and/or alignment compensation of the holder 40. In the example shown in FIG. 1, the cutting knife 12 is arranged as an extension of the output element 36.
A drive element 42 is connected at the driving hinge point 34. The drive element 42 is a connecting rod of the crank drive 16. It is connected, via a ball joint, in an articulated manner to the rocker 20. The drive element 42 is guided out of the housing 18 in a loose manner. The other end of the drive element 42, at the crank drive, follows a circular path. The loose, articulated connection to the rocker 20 enables a reciprocating movement of the output element 42.
When the counter shaft 14 is rotatingly driven, the crank drive 16 moves, via the connecting rod or the driving element 42, the second hinge point 34, in a rectilinear reciprocating movement. This reciprocating movement is transferred by the restrictingly guided rocker 20, by 90°, to the output element 36. In turn, it is transferred onto the cutting knife 12. In the shown example, the angle between the two directions of movement is 90°. The linear movement of the hinge points 32, 34 is defined by the restricted guidance of the rocking movement. Thus, no guidance of the drive and output elements 42, 36 is necessary on the housing 18. Due to the restricted movement of the rocker 20, no literal forces are produced on the output side. Thus, an exact, wear minimizing linear guidance of the cutting knife 12 is possible on the cutter bar. A transverse rotation of the rocker 20, out of the drawing plane in FIG. 1, is prevented by a two-dimensional guidance. A plane, lubricated sliding or rolling guidance, of the rocker 20 rides on a base face of the housing 18.
DE 10 2009 040 230 B4 further describes further, that two oppositely driven cutting knives are centrally driven by two such gearings.
JP 2002-156015 A describes a drive for a heald frame of a weaving machine. The driving motion of a linear motor is converted, via cranks, into a reciprocating motion of the heald frame. The heald frame is connected via hinge points to the pivotingly driven links.